An independent filmmaker who decapitated his business partner recalled yesterday how he dismembered his old buddy with a hacksaw and stashed his severed head in the freezer because he feared the victim was in the Taliban and would kill his family.

“I tried to put the [whole] body in the freezer but it wouldn’t fit. I did feel safer with the head off,” Nathan Powell, 40, said in an exclusive jailhouse interview with The Post, in which he detailed the twisted slaying of Afghan-born Jawed Wassel.

The day after the Oct. 3, 2001, killing, Powell was caught in Bethpage, L.I., trying to dump the remains. When police asked him, ” ‘Where is the friggin’ head?’ I had no idea” it was in the freezer, Powell said with a shrug. “I didn’t have a plan. I forgot it was there.”

Clad in an orange jumpsuit in Nassau County jail in East Meadow, the curly-haired killer was calm and eloquent during a 90-minute interview about why he surprisingly pleaded guilty to manslaughter on Wednesday.

With his lawyer, Thomas Liotti, by his side, Powell said he took the plea because he feared he would not get a fair trial and that he was “demonized” by the prosecution.

“I feel I would have gotten a more fair chance on trial in Afghanistan than here,” Powell said.

Powell said that Wassel had threatened to kill his wife and daughter. He said he beat him in self-defense in his Long Island City loft with a pool cue after “he struck me in the head and knocked me to the floor. He got a machete off the wall and came at me with it.”

“I hit him until the pool cue broke. I grabbed a knife and I stabbed him in the back as he was kneeling. Then I hit him again in the head with the stick. There was blood all over my daughter’s toys and books,” he said.

He said his botched body disposal proves the slaying was not premeditated.

“I was driving out here with my lights off in the middle of the night, with open boxes of body parts and a shovel in the back, I’m mumbling, and on each box was my address,” Powell said.

Liotti claimed Powell passed lie-detector tests that proved that he acted in self-defense and that Wassel had threatened Powell’s wife and child.

At the time of the murder, Powell “was suffering from post-traumatic stress syndrome” from witnessing the 9/11 attack, Liotti said.

But Nassau County prosecutor Fred Klein said Powell killed Wassel “in a surprise attack” and kept the head on ice so he could pin it on terrorists.

Klein said Wassel was not a Taliban agent but was a “patriotic American” who turned over film of his native land to the FBI to help the United States invade Afghanistan.

“The man I knew and came to be friends with was not the same man I killed that night,” said Powell.

In the plea deal, Powell will get a 20-year sentence but serve just 15.